THE QUANTUM-CHEMICAL INVESTIGATION ON THE RHODIUM CARBONYL HYDRIDE SPECIES

The electronic and geometric structures, the vibrational frequencies and the intensities of a series of rhodium carbonly hydride species were investigated by use of the ab initio calculation. It was predicted that the rhodium carbonyl hydride species containing 1, 2 and 3 hydrogen atoms could exist during the hydrogenation of CO or CO2 On Rh catalyst. H atom was tending to exclude CO out of the systems when the number of H in the system increased. In all the calculated rhodium carbonyl species, the most intensive vibrational mode, the intensify of which increased with increasing H coadsorbed, was caused by Rh-H vibration other than C-O, while an obvious counterside effect usually observed in complex compound was seen in (H)(3)RhCO[C-s]. The redshift of CO+H2Rh system from 2050 cm(-1) to about 2000 cm(-1) observed in experiments might be caused by the vibration of Rh-H instead of that of C-O, the intensity of which was predicted to blue shift and diminish with increasing H number in the rhodium carbonyl hydride species.